Intravascular occlusions requiring intervention may be treated using a variety of known medical techniques. In each of these techniques, it is desirable to provide a retrograde flow potential at the treatment site. This causes emboli that are liberated during treatment to flow in a proximal direction, so that the emboli do not travel deeper into the vascular bed and cause further occlusive events resulting in infarction and/or necrosis.
A commonly known technique for treating a vascular occlusion involves delivering lytic agents to the site of the occlusion to dissolve the occlusion. One drawback associated with such lytic agents is that they may facilitate bleeding and/or cause damage to the vessel wall.
Previously known infusion guidewires or catheters have been used to deliver such fluids to a treatment site. For example, U.S. Pat. No. 6,027,461 to Walker et al. (Walker) describes a tubular outer sheath having proximal and distal ends and a lumen extending therebetween, wherein the sheath comprises a plurality of infusion ports disposed in the sheath wall near the distal end. An integral core wire is disposed within the lumen of the outer sheath, and is affixed at a distal tip of the outer sheath to increase pushability of the outer sheath. An annulus formed between an inner wall of the outer sheath and the integral core wire defines an infusion lumen, whereby fluid may be delivered to a vascular treatment site via the infusion lumen and the infusion ports of the outer sheath.
The device described in the Walker patent has several drawbacks. First, the integral core wire, which is affixed within the lumen of the outer sheath, comprises a relatively large profile within the outer sheath, which in turn reduces the infusion lumen area and may hamper fluid transfer to the distal end of the outer sheath. The device is configured to permit the introduction of drugs or lytic agents to a treatment site, however, as noted above, the use of such lytic agents may facilitate bleeding. Additionally, the fluids that exit the infusion ports are infused into the occlusion in a direction that is orthogonal to the outer sheath, which may cause emboli that are liberated during the lytic process to travel in a direction downstream from the occlusion, thereby making them difficult to retrieve from a patient's vessel.
In view of these drawbacks of previously known systems, it would be desirable to provide apparatus and methods for treating a vascular occlusion by infusing fluid into the occlusion to dilute the occlusion and reduce adhesion of the occlusion to the intima of the vessel wall.
It also would be desirable to provide apparatus and methods for treating a vascular occlusion by infusing fluid into the occlusion in a proximal direction so that emboli generated may be urged in the proximal direction.
It further would be desirable to provide apparatus and methods for treating a vascular occlusion that utilize a centering device to assist in positioning and stabilizing an infusion catheter within the occlusion.